Minutes of 43rd FFIR meeting on 11/20/2002

The meeting was held in a room of 425 at KEK, 10:00-12:00, 11/20/2002. We discussed on beam delivery system(simulation), fast feedback system, collimation system and support tube R&D, etc. .

(1) Simulation on beam delivery system (Tanabe, University of Tokyo)

(transparencies, 4 pages, pdf ,104KB ) After the improvement of BDS-sim program, synchrotron radiations have been calculated for a comparison with the previous results. The average energies were calculated to be 0.3MeV and 2 MeV after and before the improvement, respectively, while the spatial distributions were very similar. @Smaller beam sizes with the improvement were considered to be immediate cause for smaller energies of synchrotron radiations at quadrupole magnets. In order to verify this speculation, synchrotron radiations must be@calculated individually at each magnet.@ Number of photons emitted at the nearest quadrupole magnet and the average energy were calculated to be 0.327/e and 0.433MeV, respectively, which were 1.096/e and 1.44MeV before the improvement.

For the sake of comparison, the average energy was calculated to be 0.3MeV for the NLC geometry (L*=4.3m). However, Maruyama (SLAC)'s results was 4.2MeV by GEANT3. He is making an inquiry at Maruyama about the input parameters.

(2) Collimation system(T.Ohgaki, KEK)

(transparencies, 5 pages, pdf ,996KB ) Synchrotron radiations has also been calculated by SAD (photon.sad) with Gaussian beam and flat beam of 13 sigma_x x 43 sigma_y. Both beams have energy spread of 3% (sigma of Gaussian distribution). Statistics and average energy of the radiations are listed below.

photons/eAve.energyTranspartation rate
Gaussian10890/10000 9.096MeV100%
Flat12208/10000 19.39MeV33.5%
Compared to Tanabe's calculations(Gaussian beam), more photons were generated with higher energies while the spatial distributions were very similar. Synchrotron radiations of the flat beam spread vertically (horizontally) over +/- 0.8(0.4)cm and +/- 1.0(0.8)cm at s=0 and 3.51m ,respectively, where s is a distance from IP. In these spatial distributions, various collimations are clearly seen as shadows on the radiations.

Ohgaki also is trying to replace the collimation section with previous design which Oide has made in the JLC Design Study, 1997, in order to use muon attenuators.

(3) Fast feedback system(N.Delerue, KEK)

(transparencies, 12 pages, pdf ,1.9MB ) Nicolas showed a configuration of fast feedback system at the IP for the case of L*=4.3m and 8mrad crossing together with designs of BPM and stripline-kicker for geometrical input to Jupiter-simulation (background study).

Nicolas simulated signals of BPM by using Spice program. Then, he observed real signals of a spare BPM at the end of ATF-linac. Using the signals, he tested cables for delay time, amplifiers and a hybrid circuit of HH107 for signal subtraction and split. He will design electronics circuits of the three models(simple, delayed and improved models) with these components.

The next meeting will be on 4 December (Wed.), 2002 1:00 - 3:00 pm at 3 gokan, 425.